1. Field of the Invention
The present invention relates to a device for securing a living body by pressing (hereinafter, also referred to as a “living body pressing and securing device”), and more particularly, to a living body pressing and securing device for measuring a blood pressure that can automatically wind a cuff for use in a blood pressure monitor or the like to a living body to secure the living body by pressing.
2. Description of the Background Art
To measure a blood pressure value, generally, a cuff provided with a living body pressing fluid bag for pressing an artery located within the living body is wound around the body surface, and arterial pressure pulse waves caused in the artery by inflation/deflation of the living body pressing fluid bag are detected to measure the blood pressure value. Here, the cuff refers to a band-shaped structure having a bladder, which can be wound around a portion of a living body, for use in measurement of arterial pressure of an upper limb, a lower limb or the like by introducing fluid such as gas or liquid into the bladder. Thus, the cuff represents the concept including the living body pressing fluid bag as well as means for winding the living body pressing fluid bag around the living body.
In a conventional blood pressure monitor, the cuff was wound around the living body by a subject or the like, so that there occurred variation in the cuff winding strength, which caused variation in the blood pressure values measured. Thus, in recent years, blood pressure monitors provided with an automatic cuff winding device have become widespread, which enables automatic winding of the cuff around the living body. With the blood pressure monitor provided with the automatic cuff winding device, constant winding strength is reproduced for each time of measurement, which ensures stable and accurate measurement and also eliminates the burdensome, cuff winding job.
An automatic cuff winding device mounted to a blood pressure monitor normally employs a configuration where an elastic member of an approximately cylindrical shape is arranged on the outside of a living body pressing fluid bag for pressing the living body. This elastic member is for binding and securing the living body pressing fluid bag from around the periphery, and for pressing the living body pressing fluid bag against the living body upon measurement of a blood pressure value. With the function of this elastic member, pressure loss of the living body pressing fluid bag upon measurement is reduced, and accurate measurement of the blood pressure value is ensured.
For the above-described automatic cuff winding device, a variety of mechanisms have been proposed. For example, Japanese Patent Laying-Open No. 2000-060808 discloses an automatic cuff winding device provided with a mechanism for winding a cuff around a living body by pulling an end of the cuff formed in an approximately cylindrical shape in a tangent direction. Hereinafter, this automatic cuff winding device will be described in more detail.
FIG. 16 is a front view showing a configuration of the automatic cuff winding device disclosed in the above publication. In the automatic cuff winding device shown in FIG. 16, a cuff 115 having a living body pressing air bag and a curled elastic member contained therein is wound in an approximately cylindrical shape, and attached to a base unit 151. Cuff 115 has an end 115a in a circumferential direction secured to base unit 151, and another end 115b secured to a rotary drum 155 provided at base unit 151. Rotary drum 155 is connected to an electric motor 152 with a decelerator via a pulley 153 and a belt 154. A torque limiter is also connected to rotary drum 155, to prevent a torque greater than a predetermined level from being applied to the cuff.
With the automatic cuff winding device configured as described above, electric motor 152 with a decelerator is activated to wind cuff 115 around an upper arm that is inserted into a hollow portion formed inside the cuff 115. More specifically, electric motor 152 with a decelerator drives and rotates the rotary drum 155 to carry out winding of cuff 115, and cuff 115 reduced in diameter is wound around the upper arm. In this manner, uniform winding strength is reproduced for each time of measurement, and stable and accurate measurement is realized.
Automatic cuff winding devices provided with various mechanisms, besides the one shown in FIG. 16, have also been proposed. For example, Japanese Utility Model Laying-Open No. 02-135003 discloses a winding mechanism for winding a cuff around a living body, wherein a wire rope is wound on the outside of a cuff including a living body pressing air bag therein, an end of the wire rope is secured to a pulley that is connected to an electric motor, and the electric motor is activated to drive and rotate the pulley to pull the wire rope in a tangent direction, to reduce the diameter of the cuff to thereby wind the cuff around the living body. Further, Japanese Patent Laying-Open No. 10-314123 discloses a winding mechanism for winding a cuff around a living body, wherein a tape-shaped member is wound on the outside of a cuff having a living body pressing air bag and a curled elastic member provided therein, an end of the tape-shaped member is secured to a roller portion that is connected to an electric motor, and the electric motor is activated to drive and rotate the roller portion to pull the tape-shaped member in a tangent direction, to reduce the diameter of the cuff to thereby wind the cuff around the living body.
In each of the conventional automatic cuff winding devices described above, however, the cuff itself, having a living body pressing fluid bag and/or a curled elastic member contained therein, or the wire rope or the tape-shaped member wound on the outside of the cuff, is pulled in the tangent direction to reduce the diameter of the cuff. This causes the surface of the upper arm, which is a site subjected to measurement, is pulled by the cuff in the tangent direction, and twisted. Such twisting of the upper arm would cause skin tension on the surface of the upper arm, which becomes a source of error of measurement, hindering accurate and stable measurement of the blood pressure value.
Further, the above-described winding mechanism, which winds the cuff around the living body by pulling in the tangent direction, requires a great number of mechanical components, such as a rotary drum (roller portion) for pulling the cuff itself or a wire rope, a tape-shaped member or the like, transmission means such as a pulley, a belt, a clutch and the like, an electric motor for driving and rotating the rotary drum (roller portion), a torque limiter for preventing excessive winding, and others. This not only complicates the device configuration, but also increases the device size.